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  1. #1

    Default Metallic Rap just started in OX66 Starboard Engine

    My starboard engine just developed a definitive rap this past week. It has run fine all year. Its a 2001 OX66 200HP Yamaha. No noise in neutral. Only heard under load. Gets louder as load increases. Will be taking boat to mechanic unless I can figure what it is. Pulled Spark Plugs, and they seem fine. All plugs appear the same. Checked for movement in pistons at TDC and everything seems solid. Checked, drained, and refilled LU. Some metallic fines but not excessive? Engine seems to have plenty of power, just with a rap. This engine does smoke more than the port engine, but from what I read about these 2 stroke engines, my oil usage is not excessive. I run Ring Free pretty regularly. I have had the boat for 4 years.

    What should I check before breaking down and delivering to Yamy Mechanic.?

    Thanks in advance.

  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,630

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    Pull the O2 sensor and clean it. In side the O2 mount is a part they call the Joint. It is a slide and gets filled with carbon. If it is clogged it will make a rapping noise just like a con rod.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  3. #3

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    Thanks Chris, I will inspect. Is this something that would only rap under load and not at idle? I don't notice the rap in neutral, only under load.

  4. #4
    Join Date
    Nov 2015
    Location
    brick,n.j.
    Posts
    13

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    same problem with my 02 0x66. Pulled o2 sensor cleaned joint& sensor, fixed problem. Be sure to change gaskets not reuse them.
    .

  5. #5

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    Just realized the S/N on engine reads Z200TRXY, so does the situation change if this is an HPDI? Both cowlings and other engine read LX200TRXY so I assumed both were OX66's.

    Both have O2 sensors.

    The boat is a World Cat 266. It was originally powered with Honda 130's. The previous owner repowered with rebuilt Yamaha 200's. Not sure why they would mix engines. I have had the boat for 4 years. Both seem to drink the same amount of fuel and oil, maybe with the HPDI using more oil.

    I have been doing a lot of reading the past couple of days. I would suspect that the O2's are dirty. I do run Ring Free.

  6. #6

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    I learn something every day about these engines. It looks like the Starboard engine is really an OX66 in spite of the Z200 S/N, as it has a VST like the port engine which is listed as a LX200. Interesting.

  7. #7
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,630

    Default Re: Metallic Rap just started in OX66 Starboard Engine

    Quote Originally Posted by lburess View Post
    I do run Ring Free.
    You take them apart and clean them.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

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